Linear motors find widespread use for a variety of different applications. For example, in robotic systems, linear motors are utilized to accurately position components and/or tools or other like implements, at a precise predetermined location upon a workspace. An example of such linear motor systems is set forth in U.S. Pat. No. 4,867,595 which discloses a robotic system comprised of one or more two-dimensional or X/Y linear motors, wherein, in one particular example, each linear motor is capable of picking up a component from a part feeder, carrying the part from the part feeder to a predetermined location, whereby the linear motor is accurately positioned over a location upon the workspace, and thereafter depositing the carried part upon the workpiece. The positioning accuracy of the linear motor is extremely important in order that the linear motor be accurately positioned prior to placement of the component upon the workpiece.
The linear motor disclosed in the above-identified U.S. Pat. No. 4,867,595 moves along the surface of a stator, also known as a platen, and which is typically suspended in spaced parallel fashion above the work surface of a workspace with the working surface of the platen facing downwardly. The linear motor (or motors) are positioned against the platen working surface and are normally magnetically attracted thereto. Changing magnetic fields are created by forcers provided within the movable linear motor which react with the grooved pattern in the fixed ferromagnetic working surface of the linear motor to propel the linear motor selective predetermined distances in mutually perpendicular directions over the two-dimensional workspace. A work surface is positioned a spaced substantially parallel distance below the working surface of the platen for supporting workpieces such as, for example, printed wiring boards, component receptacles and the like. Appropriate electrical and/or mechanical and/or pneumatic signals, are typically coupled to the linear motor through an umbilical cord, enabling the linear motor to perform one or a variety of functions such as component or article pick-up, placement and release, operation of a tool to act upon the workpiece and examination of the workpiece, to name just a few possible operations.
The umbilical cord may, for example, be a bundle of sleeves or conduits for conveying electrical, mechanical and pneumatic energy to the linear motor, which sleeves or conduits are arranged in a tight bundle. Alternatively, the tight bundle of conduits may be covered with a suitable covering sleeve or sheath. The first end of the umbilical cord is coupled to the sources providing the desired energy to be delivered to the linear motor arranged just beyond the workspace and the second end of the umbilical cord is coupled to an interface or connector provided upon the linear motor structure for coupling each form of energy to a desired utilization device. The linear motor is moved by signals applied through the umbilical cord to a particular X/Y location along the working surface of the stator whereupon the part or article carried by the linear motor is placed upon the work surface. Alternatively, a function such as part placement, measuring, observing, rotating a screw, soldering a joint, or the like may also be performed after appropriate X/Y positioning of the linear motor.
The umbilical cord has been found to exert a pulling force upon the linear motor which has been found to be as much as several pounds. Although this pulling force is relatively small, the pulling force nevertheless has a significant influence upon the linear motor, tending to pull the linear motor away from the highly precise position to which it has been driven. It thus becomes extremely important to prevent the umbilical cord from disadvantageously and undesirably moving the linear motor from the precise position to which it has been driven preparatory to performing a function on the work surface, said umbilical cord pulling force thereby undesirably causing a misalignment between the tool or holding device arranged upon and carried with the linear motor and the location to which that tool or holding device is intended to be aligned with.
It is thus extremely important to provide means for isolating the pulling force of the umbilical cord from the linear motor to prevent misalignment of the linear motor.